All of the patents and applications mentioned hereafter are incorporated by reference for all purposes.
Printing with ink or paint containing magnetic platelets dispersed in liquid ink or paint vehicle is known. In such applications the platelets are magnetically aligned by exposing the ink or paint upon a substrate to a magnetic field. Current examples of such prints are described by Raksha et al in U.S. patent applications 2006/0198998, 2006/0194040, 2006/0097515, 2005/0123755, and 2005/0106367.
U.S. Pat. Nos. 6,808,806, 6,759,097, 6,818,299 and 6,838,166 disclose magnetically alignable flakes and utilizing magnets for aligning flakes in printed images. More particularly U.S. Pat. No. 6,808,806 discloses the use of a flexible magnet having a cut out in a shape of a letter “F” and used for printing. In this embodiment the field emanating from the region surrounding the cut-out “F” was uniform and in a direction normal to the surface of the “F”. Flakes that were over the cut-out portion having no field were substantially flat lying. Although this embodiment provides interesting images, this invention provides additional features, not achievable with a magnet having a uniform field.
Painting with magnetic powders was employed in some industries for finishes and decorative coatings. A method for producing a magnetically formed pattern on a product is the subject-matter of U.S. Pat. No. 5,630,877. The product is produced by forming a paint layer from a paint medium mixed with magnetic non-spherical particles, and applying a magnetic field in a shape corresponding to the desired pattern to be formed. The field emanates from magnets mounted underneath the wet painted substrate. After the field aligns the particles, they are cured within the paint vehicle.
U.S. Pat. No. 6,103,361 discloses patterned substrates useful in producing decorative cookware which are formed by coating of a substrate with a base consisting of a mixture of fluoropolymer and magnetic flakes and magnetically inducing an image in the polymer coating composition. The pattern is formed by applying magnetic force through the edges of a magnetizable die positioned under a coated base to induce an image effect.
U.S. Pat. No. 6,759,097 discloses methods and devices for producing images on coated surfaces. The methods comprise applying a layer of magnetizable pigment coating in liquid form on a substrate, applying a magnetic field to selected regions of the pigment coating to alter the orientation of selected magnetic particles or flakes, and solidifying the reoriented particles or flakes in a non-parallel position to the surface of the pigment coating to produce an image such as a three dimensional-like image on the surface of the coating.
The pigment coating can contain various interference or non-interference magnetic particles or flakes, such as magnetic color shifting pigments.
U.S. Pat. No. 3,853,676 claims a pigmented film comprising a film-like material containing magnetic orientable pigment that is oriented in the field.
EP 0 710 508 A1 discloses process for production of layer that exhibits three dimensional effects through alignment of magnetic platelets.
EP 1 493 590 A1 describes a device and a method for transferring a predetermined magnetic design onto document printed with magnetic optically variable ink. The device comprises a body of a composite permanent magnet material, having a surface engraved with the pattern corresponding to the pattern of desirable indicia. The magnetic material is magnetized in the direction perpendicular to the surface. Irregularities in the surface, made with an engraving, produce changes in the direction and strength of the resulting magnetic field. These changes cause different alignment of magnetic particles in different parts of the wet ink that make possible a formation of an image with a shape corresponding to the shape of engraving.
The inventors of this invention have found that printing in accordance with the teachings of EP 1 493 590 A1 has certain limitations. For example when using color-shifting inks, a very poor color-shifting effect resulted. A disappearance of the color-shifting properties of the printed layer occurs with the repositioning of magnetic pigment particles in the layer of a wet ink along lines of magnetic field in the direction substantially perpendicularly to the surface of the document.
Notwithstanding, a color-shifting affect has the best appearance (large color travel and high chroma value) when the particles are parallel or almost parallel to the surface of the substrate. Color-shifting properties by the images printed with the device described in EP 1 493 590 makes utilization of magnetic color-shifting inks for the printing of secure documents essentially useless.
It is an object of this invention to provide a magnet that is more simple to manufacture and offers a high degree in flexibility with regard to the field generated by the magnet.
The magnet does not require costly and difficult carving or removal of material so as to vary the field.
In image of object, logo or indicia is made within the magnetic material of a block or sheet so that the magnet will provide a field that corresponds the object, logo, or indicia when the field is used to align flakes in paint or ink.
The image within the magnetic material is not visible to the eye, but is coded into the magnetic material so as to generate a field that corresponds to the object logo or indicia that is used to “code” the magnetic material.
Advantageously, the object, logo or indicia encoded into the magnet cannot be seen, but is present and generates a magnetic field that aligns flakes placed on a substrate in the field to replicate the object, logo or indicia.
Advantageously a common “fridge” magnet can be encoded with magnetic information so as to change its field direction to form an image.
Advantageously this encoded magnet may be of flexible magnetic material and can be placed on a drum and used to “print” images within a wet inked or painted substrate by aligning particles in a manner that reflect the encoded magnetic information.
As will be described hereafter, prior art methods of applying a magnetic field to inks and or paints that have alignable flakes therein, includes the use of recessed or embossed magnetic regions. In contrast this invention utilizes a magnet having a flat surface wherein magnetic and non-magnetic, or differently magnetized regions are provided within a single monolithic magnet that cause alignment of flakes forming images in a liquid in having field alignable flakes. Advantageously having a flat die or magnetic printing head or plate that is magnetized within eliminates problems associated with making and using 3-D magnetic forms. The flat die can be brought into intimate contact with the substrate and even if pressure is applied the result will be substantially the same. This is not the case with 3-D embossed or engraved magnetic printing plates. As well, boundaries within the printed image can be made sharper with more ease then with embossed or recessed magnetic printing plates.